KC, I just love the idea of a frame mount, but don't feel the parts are good enough yet for reliability, day in and day out.
I don't build with or on crap either, which is why you'll never see a build on a Huffy by me.
The HS 142F 49cc 4-stroke is a direct copy and suitable replacement of the venerable Honda 50cc workhorse you see powering portable generators, pumps, etc.
Keep the oil fresh and they will run all day long every day for years.
The direct drive kit is pretty good, but the SBP shift kit replaces many of the parts.
The Sick Bike Parts jackshaft kit is pretty flexible but it did have small issues that Paul and Jim are working out as did the 4G belt drive which Don Grube and I have already worked out regarding sprocket freedom on the output shaft and in production now.
If you really want to go 'no muss, no fuss' reliable have you considered electric?
Just finished this up and have a few more days to test it before the customer picks it it.
~$1300 retail for everything but the bike with that big LI triangle battery pack.
That's a full suspension, 9-speed, dual disc ~$3500 customer supplied Specialized bike by the way but you can go much less expensive like this.
Same motor, controller, and SBP shift kit, just a smaller battery and different bike.
It was for a petite woman so a 24" Macargi Rover 3-speed bike and 600W 'bottle' LI battery complete with bike for under $1300.
I guess I'm just a symmetry kind of builder with a low center of gravity mindset, I don't like stuff above the bottom of the seat or hanging off the side when possible.